Efficiently and reliably indentifying the accessibility of femtocells in heterogeneous networks

To deploy more base stations (BSs) to enhance the capacity is one of the popular solutions to meet the explosive wireless traffic requirements. Femtocells, which are low power BSs typically installed in home or small office, are getting increasing support to be deployed and launched. Femtocells can provide access to closed or open group of uses. When a femtocell belongs to a closed subscriber group (CSG) which only allows mobile stations (MSs) who subscribe the CSG to access, femtocell needs to broadcast its CSG identifier (CSG ID) for MSs to check whether they have the accessibility. The CSG ID can be of many bits (e.g., 24 bits), and it has high cost to broadcast CSG ID as the payload in the broadcast channel (BCH) which is very expensive resource. In this paper, we propose a novel solution to carry CSG ID by scrambling the CSG ID with the cyclic redundancy check (CRC) of the BCH. The proposed solution not only achieves higher efficiency by reducing extra overhead supposed to be added by CSG ID to the BCH payload, but also achieves enhanced CRC capability for the original BCH, i.e., enhanced reliability, compared with the design of carrying CSG ID in the BCH payload. Based on analysis, we prove the advantage of our solution. We also reveal the theoretical rationale behind, based on which our idea can be extended.